The invention may be applied, in particular, when the vehicle in question is a robot designed to carry out work under conditions that are hostile to man. Such work may consist, for example, in reconnaissance, surveillance, repair, or cleaning operations. To perform such operations, the robot may be equipped with appropriate equipment, such as video cameras, measuring instruments, and tools. For example, such a robot may be useful in a nuclear facility subjected to high intensities of ionizing radiation after an incident, in the chemicals industry when there are risks of explosion, in agriculture, or in military activities.
Such a robot must be capable of moving over uneven terrain. To this end, it may be provided with wheels, legs, and/or crawler track drive units, that are fixed or moving relative to a vehicle body.
The robot must also be capable, preferably without human assistance, even remote, of navigating, i.e. of determining its position as accurately possible and at any time. Generally speaking, such a robot cannot use points of reference defined relative to the terrain for the purposes of providing such navigation. On-board navigating apparatus must then measure the displacement of the robot from a known starting point. Such a measurement is taken by integrating the components of a velocity vector measured at all times.
To this end, it is known for velocity measuring apparatuses to be used. Such apparatuses include inertial units co-operating with odometer counters to determine the velocity and the position of a vehicle having four wheels or two crawler track drive units. Velocity and position are determined by merging "inertial" or "accelerometer" data with odometer data resulting from counting wheel revolutions. Such data needs to be merged because the accelerometer data is inaccurate and requires position measurements to be regularly re-adjusted whenever they are obtained by double integration of accelerometer measurements.
Despite such data-merging, measurements made by known apparatuses remain subject to major errors under the usual conditions in which the above-mentioned work robots are used.